1. Field of the Invention
The invention relates to a display apparatus and a light source, and more particularly, to a liquid crystal display apparatus and a backlight module.
2. Description of Related Art
With the advancement of technology, a flat display becomes a mainstream of the display device to replace a conventional cathode ray tube (CRT) having a big volume and heavy weight. In flat displays, liquid crystal display (LCD) is popular with people. The LCD includes a liquid crystal panel and a backlight module but is unable to emit light spontaneously. The liquid crystal panel is used to determine a light transmittance. Thereby, the backlight module is disposed on the backside of the liquid crystal panel to serve a surface light source for the liquid crystal panel. A display quality of the LCD is influenced by an optics quality of the surface light source greatly. For example, in order to display frames normally and decrease distortions, a uniform surface light source is necessary. In addition, in order to increase a brightness of the frames, a light emitting angle range of the surface light source is limited to avoid light loss.
In a conventional transmissive side incident type backlight module, a lower diffusion sheet, two prism sheets and an upper diffusion sheet are disposed on the light guide plate sequentially from bottom to up, wherein prism rods of one prism sheet are perpendicular to prism rods of the other prism sheet. The prism sheet is used to decrease light emitting angle range, the upper diffusion sheet and lower diffusion sheet are used to uniform the light and avoid moire being generated by a contour of the prism rod and the liquid crystal panel. However, such a method that four optical films are disposed in the light guide plate increases the cost of the backlight module, and too many optical films also obstruct fabrication and it is hard to decrease a thickness of the backlight module.
Besides, a transmissive LCD is usually used in an indoor environment. If the transmissive LCD is used in an outdoor environment, an ambient light is too strong to identify the frames displayed by the transmissive LCD. Furthermore, in the outdoor environment, users may easier see the frames displayed by a reflective LCD. For the reflective LCD, a back light source is unnecessary, so that the reflective LCD has a property of low power consumption.
However, when a strong light strikes a surface of the reflective LCD, the reflective light is also too strong to identify the frames. Presently, although a transflective type LCD is developed to adapt to the indoor environment and the outdoor environment, the problem that the users may not easily see the frames caused by the strong ambient light and the strong reflective light is not over come.
On the other hand, U.S. Pat. No. 7,374,328 provides an optical film including a diffusion layer, a reflective layer, and a lens layer. The reflective layer has openings corresponding to the lens layer, the light emitted by the light source sequentially passes through the diffusion layer, the opening, and the lens layer. Moreover, each of the Taiwan patent application publication No. 200808478, U.S. Pat. No. 6,633,351, and U.S. Pat. No. 6,967,779 provides an optical film and manufacture method of the optical film. Taiwan Patent No. 561278 and U.S. patent application publication 20070002452 both disclose an optical film, and U.S. Pat. Nos. 6,961,108 and 6,909,486 disclose a transflective type optical film.